As I have a much larger irrigation system, this would not be a viable option at this location (nor at any of the houses I've owned)..
It would depend on your scale of irrigation and the length of the main supply lines. If your water source is quite distant from your lateral lines, and the supply pipe you use is expensive then it would save money on installation. That is because it would halve the number of supply lines and valves. The usual approach to small and large scale irrigation is to run zone lengths according to flow and pressure available. I set the length and number of sprinklers to the max the flow and pressure allows. Each zone has to be provided with a mains supply line. By using a common supply line for each pair of zones I only need 1 valve and 1 supply line.
The savings are only gained at installation. Another application is where the water pressure at a site has fallen due to say loss of aquifer pressure or more people drawing on the source. The irrigation system can be remediated by splitting each zone and adding the valve. This essentially creates smaller zones that can be alternated without adding more supply line using the existing flow and pressure.
That is basically what I did in my garden. I could not run a 5 sprinkler zone. Instead of installing 2 zones and 2 solenoids I installed the valve to create alternating subzones. Saved a solenoid (in fact I just use a single battery timer) and saved supply pipe.
Thank you for your comments though.
